1. Field of the Invention
The present invention relates to an apparatus for controlling operation reaction which controls the magnitude of an operating reaction of a winch such as a crane.
2. Prior Art
Means for controlling the magnitude of an operating reaction of an operating lever according to a lifting load is well known as disclosed in Japanese Utility Model Publication NO. 3976/1983, in which a load pressure of an actuator (hydraulic motor) acting on a spool of a direction control valve is fed back to an operating valve operated by an operating lever to thereby apply an operating reaction corresponding to the lifting load to the operating lever.
In addition, means is well known as disclosed in Japanese Utility Model Publication No. 14077/1987, in which reaction devices each comprising an expansion cylinder and a spring provided at the end of a rod of the expansion cylinder are arranged symmetrically on opposite sides in an operating direction of an operating lever, the expansion cylinder being extended according to a lifting load detected by a load detector to bring the spring into contact with the operating lever so as to obtain an operating reaction by the force of the spring.
However, in any of the aforementioned prior art, only the lifting load is used as the condition for deciding the reaction, and the reaction is decided irrespective of the extent of the lever operating amount. Therefore, for example, in the inching work in which the lever is operated with a small operating amount in order to mincingly wind up a lifting load, the same reaction as that of normal winding-up work acts, thus making the operation difficult, resulting in a poor operability. Despite the act that the winch load is determined by the lifting load and the winding-up speed lever operating amount), the aforesaid system for detecting only the winch load has a drawback in that proper reaction control according to the winch load cannot be achieved.